Friday, 1 October 2010 - Monthly Climate Summary for Tasmania - Product code IDCKGC17R0
Tasmania in September 2010: Cold, snow to low levels, flooding and huge waves
Though few temperature and rainfall records were broken in Tasmania during September, there were many interesting weather events. Huge waves were generated by a deep low on the 16th, snow fell to low levels on several days and heavy rain in the north caused flooding on the 4th. There were several very cold days and nights, and few mild ones.
- Rainfall above average except for the upper east
- Temperatures below average overall
- Westerlies with cold fronts for much of the month
Huge wavesThe waverider buoy off Cape Sorell on
Tasmania’s west coast registered an 18.4 metre wave at
about 11 am on the 16th. This approaches the record wave of 19.8 metres
measured by a similar buoy operated by CSIRO in July 1985.
The peak was a single wave, but for most of the 16th waves at the buoy
were averaging over 8 metres. The observers at Maatsuyker Island just
Tasmania’s south coast reported an exceptional 11 metre
swell, and at Cape Bruny 10 metres
was reported. The huge waves were generated by strong winds around a
deep low pressure system over the
Southern Ocean south of Tasmania as a cold front swept across the
state. The same system brought damaging winds, rain, hail and snow,
with road closures, building damage and failed power lines reported
across the state. Wind gusts reached 148 km/h at Maatsuyker
Island and 141 km/h at Cape Bruny. A few days later the same
system brought extreme weather to New
Heavy rain and flooding
Heavy rain fell across most of Tasmania on the 4th as a deepening low pressure system approached from the northwest then crossed the state overnight. By 9 am, 15 to 25 mm had fallen in the northwest with light falls elsewhere. The rain continued during the day, with a further 81 mm at Mount Victoria, 75 mm at Mount Barrow and 63 mm at Mount Read during the next 24 hours, causing flooding of most rivers across northern Tasmania. In total, over 50 mm fell in most of the north, west and far south, with near 100 mm on higher ground in the northeast.
Mostly wet overall
After the heavy rain on the 4th, the weather pattern over Tasmania was nearly always westerly with cold fronts crossing the state regularly. From the 10th it rained every day in the west, and showers extended to most other areas with each front. This meant it was wetter than usual in all but the upper east. Monthly totals graded markedly across the state, from a high of 549 mm at Mount Read in the west to just 18 mm at Swansea in the east. Some areas had nearly double the September average, and Lunawanna (on Bruny Island) had its wettest September since 1984.
Cold days and nights with snow to low levels
There were several very cold days and nights during September. Mount Wellington had the two coldest days for the state so far this year, not rising above -2.2 °C on the 28th and -2.1 °C on the 29th. Liawenee fell to -7.9 °C on the morning of the 7th, equalling the coldest temperature recorded during winter. Liawenee also fell below -7 °C on the 3rd and 8th: never before has it had so many nights this cold in September. Other sites had their coldest September day or coldest night in many years including Dover, which had its coldest September morning on the 8th, and many sites in the south on the 15th. The cold was accompanied by snowfalls to low levels on the 15-16th and 28-29th, something that is uncommon at this time of year and contrasted with a relatively mild winter.
For the whole month, daytime temperatures were mostly one to three degrees cooler than usual in the west and south and slightly cooler than usual elsewhere, while minima were near average. It was the coldest September since at least 2003 for most sites, and Strathgordon had its coolest mean maximum temperature on record for September.
In with the cold weather there were a few days and nights that were warmer than usual, generally when fronts were crossing the state overnight or it was fine during the day. The 20th was especially warm in the north and east with temperatures around 20 °C. Swansea reached 21.7 °C on this day, the warmest temperature in Tasmania for the month, and Devonport reached 19.6 °C, its highest September temperature in 19 years of record. The warmest nights were the 5th, 25th and 27th, when temperatures didn't drop below 10 °C in many areas.
Hobart: wet and windy with many cold nights
It was a wet and windy September in Hobart. A total of 88 mm of rain was recorded for the month, less than the 133 mm that fell last year but still 35 mm more than the long-term average. As with most of Tasmania, the heaviest rain fell on the 4th when 27 mm was recorded in 24 hours. After the westerlies kicked in around the 10th, most days in Hobart were windier than usual, especially on the 15th to 18th and 27-28th. There were three days when gusts exceeded 90 km/h, an equal record for September.
There were many cold nights in Hobart with the temperature dropping below 4 °C ten times, nearly double the normal for September and something that hasn't happened for over 15 years. The coldest temperature was 1.7 °C on the 7th, Hobart's coldest September morning since 1995. There were also a number of cold days, the coldest being 10.5 °C on the 28th (although on the 16th the temperature was below 6 °C for much of the afternoon). The cold was tempered by some warm periods from the 9th to the 12th and 23rd to 26th, so that over the whole month mean temperatures were near normal. The warmest day was 18.9 °C on the 26th and the warmest night was 11.9 °C on the 25th.
for the year to date in Hobart are still very warm: the mean daily
maximum temperature of 17.9 °C for this period is the highest in over
120 years of record.
|Extremes in September 2010|
21.7 °C at Swansea Post Office on the 20th|
|Warmest days on average||16.3 °C at Bicheno (Council Depot)|
|Coolest days on average||
3.3 °C at Mount Read|
-2.2 °C at Mount Wellington on the 28th|
-7.9 °C at Liawenee on the 7th|
|Coolest nights on average||-1.8 °C at Mount Wellington|
|Warmest nights on average||
9.0 °C at Swan Island|
12.6 °C at Scamander on the 25th|
|Warmest on average overall||
11.9 °C at Eddystone Point|
|Coolest on average overall||0.9 °C at Mount Wellington|
549.2 mm at Mount Read|
|Driest overall||18.4 mm at Swansea Post Office|
81.4 mm at Mount Victoria (Una Plain) on the 5th|
|Highest wind gust||
148 km/h at Maatsuyker Island Lighthouse on the 15th|
Click on a map to show it full size in a pop-up window
|Highest total September rainfall for at least 20 years|
for September 2010 (mm)
Most recent September
at least this wet
|Record lowest September mean daily maximum temperature|
Mean daily maximum
for September 2010 (°C)
|Strathgordon Village||9.3||9.5||in 1970||28||11.5|
|Lowest September mean daily maximum temperature for at least 20 years|
Mean daily maximum
for September 2010 (°C)
Most recent September
at least this cool
|Maatsuyker Island Lighthouse||10.2||=10.2||in 1970||40||12.2|
|Butlers Gorge||8.1||7.9||in 1969||24||10.1|
|Record lowest September temperature|
in September 2010 (°C)
|Dover||-2.1||on the 8th||-1.0||on the 9th in 1992||21||4.9|
|Summary statistics for September 2010|
|Northern (district 91)|
|Bridport (Sea View Villas)||14.2||-0.5||19.0||21st||6.1||-0.7||0.6||29th||78.0||76.5||average||102%|
|Burnie (Round Hill)||14.2||-0.1||19.4||21st||7.4||+0.6||2.3||29th||96.6||87.7||average||110%|
|Cape Grim BAPS||12.6||-0.8||14.7||12th||8.2||-0.4||4.3||3rd||100.8||77.0||high||131%|
|Cressy Research Station||14.1||-0.6||19.3||20th||4.0||+0.1||-2.5||8th||57.0||63.8||average||89%|
|Launceston (Ti Tree Bend)||15.3||-0.2||19.4||20th||5.1||-0.1||-0.6||30th||78.0||67.1||average||116%|
|Luncheon Hill (Forestry)||11.0||-1.3||15.2||21st||4.7||-0.7||1.1||29th||192.2||179.6||average||107%|
|Scottsdale (West Minstone Road)||13.5||-0.7||18.3||20th||4.5||-0.2||-2.2||30th||128.0||99.5||high||129%|
|Sheffield School Farm||12.4||-0.7||19.3||20th||4.4||-0.3||-0.9||30th||127.6||128.6||average||99%|
|East Coast (district 92)|
|Bicheno (Council Depot)||16.3||+0.2||20.0||25th||7.1||-0.3||1.7||8th||21.8||44.4||low||49%|
|Fingal (Legge Street)||14.5||-0.8||20.4||20th||3.0||-0.3||-3.2||30th||22.2||49.6||low||45%|
|Lake Leake (Elizabeth River)||10.7||-0.6||17.3||20th||1.7||-0.3||-3.8||2nd||53.2||71.0||average||75%|
|Maria Island (Point Lesueur)||14.4||18.0||25th||7.8||3.2||29th||47.4|
|Orford (Aubin Court)||14.7||-1.0||19.6||26th||5.7||+0.2||-0.4||8th||54.8||51.9||average||106%|
|St Helens Aerodrome||15.8||21.1||20th||6.4||0.7||14th||21.8|
|Swansea Post Office||16.1||+0.1||21.7||20th||6.3||+0.5||-0.7||8th||18.4||40.9||low||45%|
|Midlands (district 93)|
|Ross (The Boulevards)||13.9||-0.5||20.4||20th||3.4||-0.3||-4.6||7th||34.6||53.7||average||64%|
|Southeast (district 94)|
|Cape Bruny (Cape Bruny)||12.6||-1.8||17.3||9th||6.3||-1.2||2.5||28th||131.4||70.8||v high||186%|
|Cape Bruny Lighthouse||12.3||-0.9||16.5||9th||6.4||-0.6||2.3||28th||142.8||81.2||v high||176%|
|Geeveston (Cemetery Road)||12.8||-2.0||16.1||25th||5.3||+0.9||-1.2||3rd||152.8||93.4||high||164%|
|Grove (Research Station)||13.5||17.4||12th||4.1||-3.1||3rd||157.0|
|Hobart (Ellerslie Road)||14.8||-0.3||18.9||26th||6.6||+0.2||1.7||7th||88.2||53.4||high||165%|
|Maatsuyker Island Lighthouse||10.2||-2.0||13.0||12th||6.3||-0.5||2.6||14th||136.4||109.5||high||125%|
|Melton Mowbray (North Stockman)||12.8||-1.8||17.5||26th||4.3||-0.1||-2.6||7th||62.2||55.3||average||112%|
|Tunnack Fire Station||11.3||-1.2||16.5||26th||2.8||-0.5||-4.3||7th||86.8||68.0||high||128%|
|Derwent Valley (district 95)|
|Bushy Park (Bushy Park Estates)||14.3||-1.1||18.5||26th||4.2||+0.3||-3.5||8th||106.8||54.3||v high||197%|
|Maydena Post Office||11.0||-2.7||16.0||21st||3.1||-0.3||-2.0||3rd||179.2||142.2||high||126%|
|Ouse Fire Station||13.7||-2.1||17.6||12th||4.6||+0.9||-3.9||8th||103.6||75.7||high||137%|
|Central Plateau (district 96)|
|Lake St Clair National Park||8.5||-1.5||12.6||7th||0.9||+0.1||-4.9||8th||272.4||216.2||average||126%|
|West Coast (district 97)|
|Hartz Mountain (Keoghs Pimple)||5.9||-2.8||11.8||7th||0.7||-1.1||-2.6||28th||140.2||102.0||high||137%|
|Scotts Peak Dam||9.7||-2.6||15.9||21st||3.2||-1.1||-1.6||8th||310.2||219.3||high||141%|
|Strathgordon Village||9.3||-2.2||13.7||21st||3.9||-0.5||-0.5||3rd||462.3||281.1||v high||164%|
|King Island (district 98)|
|King Island Airport||13.7||-0.9||15.5||25th||8.3||0.0||3.7||2nd||74.0||88.3||average||84%|
|Flinders Island (district 99)|
|Flinders Island Airport||14.2||-0.9||16.6||4th||8.3||+0.8||-0.1||8th||37.6||63.9||low||59%|
|Antarctica and Macquarie Island (district 300)|
A Monthly Climate Summary is prepared to list the main features of the weather in Tasmania using the most timely and accurate information available on the date of publication; it will generally not be updated. Later information, including data that has had greater opportunity for quality control, will be presented in the Monthly Weather Review, usually published in the fourth week of the month.
This statement has been prepared based on information available at 10 am on Friday 1 October 2010. Some checks have been made on the data, but it is possible that results will change as new information becomes available.
Averages are long-term means based on observations from
all available years of record, which vary widely from site to site.
They are not shown for sites with less than 10 years of record, as they cannot then be calculated reliably.
The median is sometimes more representative than the mean of long-term average rain.
The Rank indicates how rainfall this time compares with the climate record for the site,
based on the
(very low rainfall is in decile 1, low in decile 2 or 3,
average in decile 4 to 7, high in decile 8 or 9
and very high is in decile 10).
The Fraction of average shows how much rain has fallen this time as a percentage of the long-term mean.